The instant invention is directed to the field of security control and, in particular, to the electronic acquisition of optical fingerprint images and the accurate and repeatable storage thereof.
Prior art techniques for obtaining fingerprints have included application of ink to a person""s fingertips and rolling or simply pressing the tips of the individual""s fingers to appropriate places on a recording card. This system has severe limitations, the least of which is the use of ink which can often require several attempts before a usable image is obtained. Furthermore, use of an ink-based system requires cooperation of the individual from whom the prints are being taken, since blurring and smearing of the prints often occurs when attempts are made to obtain fingerprints from a hostile individual. Additionally, it is difficult to easily adapt inked prints for computerized storage and retrieval; thus making it difficult for various governmental agencies to reliably transfer and share data.
Several attempts have been made to optically acquire fingerprint images, however known systems have various drawbacks. In order to record data correctly, it is necessary to utilize trained personnel to aid the individual in guiding his/her fingers over the optical reading area. The fingers must be accurately positioned and the rate of rotation of the fingers must not exceed the recording abilities of the device. If the fingers are not rotated at the correct speed, data will be lost necessitating repeating of the entire procedure.
Several of these systems generate an optical image in real time, but they suffer from errors caused by their need to approximate the complete fingerprint image by electronically combining a plurality of smaller images or xe2x80x9cslicesxe2x80x9d and smoothing the edges of the slices together to form an image which has the appearance of a full fingerprint. In performing the smoothing operation, a composite image is created which averages the data contained in the adjacent image slices, discarding discontinuities and artifacts so as to arrive at what can be described as a xe2x80x9cbest guessxe2x80x9d image.
Improvements on this so-called xe2x80x9cbest guessxe2x80x9d scenario have sought to provide overlapping slices wherein the image is formed by generating a composite array as a mathematical function of a comparison and an average of the overlapping data which constitutes the overlapping portions of adjacent slices. While this method more accurately characterizes transitions between the boundaries of adjacent image slices, the averaging of discontinuities and discarding of artifacts continues to prevent the obtention of images having the desired degree of accuracy and resolution. Such images still engender a degree of inaccuracy which, when coupled with the limits of resolution and recording inherent in the available hardware, render them unacceptable.
U.S. Pat. No. 4,933,976 discloses method for generating data characteristic of a rolled fingerprint image. The method requires storing arrays of digital data characteristic of adjacent and overlapping fingerprint images of portions of the finger as the finger is rolled across an optical device, the optical device capturing the image and generating a composite array of digital data characteristic of a rolled fingerprint image as a mathematical function of overlapping image portions of the fingerprint.
What is lacking in the art is a method and apparatus for reliably recording accurate high resolution electronic optical images of fingerprints without the necessity of adhering to critical sampling procedures. Such an invention would enable an untrained individual to accurately record fingerprint images which do not inherently contain unacceptable errors due to averaging of the image while processing.
The present invention is an improved method and apparatus for acquiring a high resolution electronic optical image of fingerprints. These images are then stored and indexed in a database which can be readily accessed by governmental agencies such that an individual can be easily identified. The invention employs the concept of moving a fingerprint over a viewing area and knitting the image together, in accordance with a simultaneously scanned and uniquely designed bar code.
By utilizing the bar code as a caliper, it is now possible to accurately and repeatable record and store high resolution optical images of fingerprints with no apparent loss of accuracy owing to the electronic knitting process. The caliper enables the microprocessing device to positively identify and organize each of the individual slices which make up the final image. It then becomes possible for an individual to rotate their fingertip in a back and forth motion, without concern for rotation speed, until such time as the device acquires accurate data for all of the required slices. The microprocessing device is then able to reassemble the recorded data by matching said data to the particular segments delineated by the fixed caliper gradations, and knitting the appropriate slices together so as to form a complete image of the fingerprint with minimal loss of resolution.
Thus, it is an objective of the present invention is to provide a method and apparatus whereby an untrained individual can accurately record electronic optical images of their fingerprints.
An additional objective of the present invention is to provide a method and apparatus whereby a fingerprint verifier has a mechanism to slide a prism over an imaged area of a camera. The position of the prism being determined by a binary absolute linear code on a sliding mechanism imaged by the same camera at the side of the fingerprint wherein the images are knitted together to simulate a large CCD.
It is an additional objective of the invention is to provide a method and apparatus whereby individual segments of data, having the attributes of portions of the image of a fingertip, may be accurately recorded in a random fashion and then reassembled so as to produce an accurate and coherent image of the original fingerprint.
Still another objective of the invention is to provide an apparatus that will operate in two modes, a) Roll print and b) 4 finger flat (which covers two thumbs).
Yet still another objective of the invention is to provide an apparatus that does not have a real time element allowing a user to roll as fast or as slow as they feel comfortable.
Another objective of the invention is to provide an apparatus whereby the individual drives the scanner mechanism, thereby eliminating the cost of a motor or the like drive mechanism for moving fingers over the scanner, or the scanner past the fingers.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.